Wireless communication system capable of saving time for mutual data communication in sniff mode

ABSTRACT

A wireless communication system capable of saving time for mutual data communication in a sniff mode. The wireless communication system has: a master apparatus for calculating a sniff parameter including a time of a sniff period capable of performing the communication by allowing a corresponding device to commonly have the time in the sniff mode, when a communication mode for a mutual data communication by a user is selected to be operated in the sniff mode; and a sniff slave apparatus for performing the mutual data communication with the master apparatus by commonly having a corresponding time calculated in accordance with the sniff parameter. At this time, the sniff parameter includes at least one among a cyclic information, an allocated time information of the sniff period, and a start time information in which the master apparatus communicates with the sniff slave apparatus operated in the sniff mode.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a wireless communication apparatus, andmore particularly, to a wireless communication apparatus capable ofperforming a mutual communication according to a sniff parametercalculated based on the information with respect to sniff slaveapparatuses connected with a master apparatus in a sniff mode forperforming a communication for a determined time between the masterapparatus and the slave apparatuses. The present application is based onKorean Application No. 2001-53176, filed Aug. 31, 2001, which isincorporated herein by reference.

2. Description of the Related Art

Bluetooth is a communication technology capable of transmittingwirelessly information such as letter data, sound data, and video dataat a distance of 10 to 100 m.

A Bluetooth apparatus, which can mutually communicate according to theBluetooth communication method, sets up a connection status thatcommunicates through operations such as an inquiry, an inquiry scan, apage, and a page scan. From this process, a master apparatus and a slaveapparatus are determined according to their respective roles.

When a new connection status is set up between the Bluetoothapparatuses, an operation clock and a frequency pattern should beadjusted between the Bluetooth apparatuses. In the process for settingup the connection status, the inquiry is an operation of repeatedlysending an operation frequency from the master apparatus so that theslave apparatus can adjust the frequency pattern with the masterapparatus. The inquiry scan is a process performed in the slaveapparatus. The inquiry scan detects a transmitted frequency, and adjustsa synchronism with the detected frequency. The page is a process forsending a clock signal from the master apparatus so that the slaveapparatus can adjust for the operation clock of the master apparatus.The page scan is used to detect the transmitted clock signal and toadjust the synchronism thereby. The page scan is done by the slaveapparatus. A network, which is formed by two or more slave apparatusessetting up the connection status in regard to the master apparatus, is aPiconet.

According to the Bluetooth communication method currently in use, amaster apparatus can communicate with seven slave apparatuses byconnecting the slave apparatuses to achieve an active status in thePiconet. Moreover, to connect a new slave apparatus to the Piconet, themaster apparatus terminates the active status with respect to one slaveapparatus among the seven slave apparatuses, and performs acommunication connection in the active status with the new slaveapparatus.

On the other hand, in the Bluetooth communication method, the masterapparatus and the slave apparatuses are operated in an active mode forperforming a normal communication with the slave apparatuses, and in ahold mode, a sniff mode, and a park mode which enables the communicationapparatus to conserve power. The hold mode is a typical mode used whenthere is no need to send data for a relatively long period. The sniffmode is a mode for transmitting data from a certain time mutually set upbetween the master apparatus and the slave apparatuses for apredetermined time. The park mode is a mode for performing mutualcommunication between the master apparatus and the slave apparatusintermittently to allow the slave apparatus to synchronize with themaster apparatus, and to acquire conversion to the active mode.

The slave apparatuses, which operate in one of the hold mode, the sniffmode, and the park mode, communicate with the master apparatus for apredetermined time during the operation time of the slave apparatusesoperated in the active mode. A data transmission period (hereinbelow,referred to as a ‘sniff period’) of the master apparatus and the slaveapparatuses according to the sniff mode is repeatedly generated at apredetermined cycle until the slave apparatuses operated in the sniffmode are converted to the active mode.

At this time, each of the slave apparatuses operated in the sniff modecan have a start time, an allocated time of the sniff period, and asniff period generation cycle (hereinbelow, referred to as a ‘sniffparameter’), respectively different. The sniff parameter is determinedthrough a link management protocol (LMP) among Bluetooth protocol levelstructures. The master apparatus of the Piconet including the slaveapparatuses (hereinbelow, referred to as ‘a sniff slave apparatus’)operated in the sniff mode allocates the different sniff parameters tothe sniff slave apparatuses, and stores the differently allocated sniffparameters.

Accordingly, the master apparatus scheduling the data communication witheach of the slave apparatuses needs a memory packet for storing thesniff parameter allocated to the slave apparatuses operated in the sniffmode. Therefore, a number of memory packets should be providedcorresponding to at least the number of the slave apparatuses operatedin the sniff mode. For example, when seven sniff slave apparatuses areconnected with one Piconet, seven memory packets for storing the sniffparameter allocated to the seven sniff slave apparatuses are needed. Inaddition, seven sniff time sheets (hereinbelow, referred to as a ‘snifftimer’) for notifying the end of the corresponding sniff period to acontroller (not shown) of the master apparatus by checking the timerwith respect to the sniff period of each of the sniff slave apparatusesare disposed at the master apparatus in the conventional sniff mode.

In the meantime, it will sometimes happen when communicating between themaster apparatus and the slave apparatuses through the conventionalsniff mode that the sniff period is not allocated to the correspondingsniff slave apparatuses due to a cyclic operation having a higherpriority level than the sniff slave apparatuses. The inquiry, theinquiry scan, the page, and the page scan, which are performed by themaster apparatus and the slave apparatuses in the Piconet, are suchcyclic operations. A supervision timeout rule, which stops the operationneeded for the communication connection when a predetermined time set upfor communication connection has passed, is applied in the Bluetoothcommunication method. Accordingly, when the operation, which is neededfor the communication connection during the sniff period allocatedbetween the master apparatus and the slave apparatuses, is notsupported, the communication connection between the master apparatus andthe slave apparatuses fails.

As an example of the communication apparatus utilizing the Bluetoothcommunication method is a personal portable terminal. Thus, memorypackets corresponding to the number of the personal portable terminalsoperated in the sniff mode should be provided in each of the personalportable terminals. But it is not desirable to provide such memorypackets, because this makes it difficult to reduce the size of theproduct and causes an increase in production costs. Moreover, since themaster apparatus consecutively performs the data communication throughthe sniff parameters stored in each of the memory packets, thescheduling time for the data communication is increased.

The scheduling time for the data communication of the master apparatusis increased, since the master apparatus should allocate the sniffperiod in regard to each of the sniff slave apparatuses after findingthe period not having a cyclic active operation when there is the cyclicactive operation performed by the Piconet master apparatus.

SUMMARY OF THE INVENTION

The present invention has been made to overcome the above-mentionedproblems. Thus, the object of the present invention is to provide acommunication apparatus capable of reducing the amount of memory packetsfor storing a sniff parameter according to a sniff mode by setting up asniff period that slave apparatuses connected with a master apparatuscan commonly use so that the master apparatus and the slave apparatusescan perform a communication connection in the sniff mode.

Another object of the present invention to solve the above problem is toprovide a communication apparatus that controls each of the slaveapparatuses connected with a master apparatus to perform thecommunication with the master apparatus for an allocated timecorresponding to a set-up sniff period.

Another object of the present invention to solve the above problem is toprovide a communication apparatus capable of simplifying a communicationscheduling operation of a master apparatus for a data communication ofthe master apparatus and sniff slave apparatuses in a sniff mode.

The above object is accomplished by providing a wireless communicationsystem comprising: a master apparatus for calculating a sniff parameterincluding a time of a sniff period capable of performing a communicationby allowing a corresponding device to commonly use the time in a sniffmode, when a communication mode for a mutual data transmission by a useris selected to be operated in the sniff mode; and a sniff slaveapparatus for performing the mutual data transmission with the masterapparatus by commonly using a corresponding time calculated inaccordance with the sniff parameter. The master apparatus performscommunication scheduling for the data communication of the sniff slaveapparatus, when the sniff parameter is calculated. The sniff parameterincludes a cyclic information in which the master apparatus works in thesniff mode, allocated time of the sniff period, and start timeinformation. Moreover, it is preferable that the master apparatusperforms data scheduling for data communication of the sniff slaveapparatuses when the sniff parameter is calculated.

Preferably, the master apparatus includes: a parameter storage unit forstoring the sniff parameter; a time counting unit for allowing themaster apparatus to count a time during an allocated time of a sniffperiod according to the sniff mode based on an operation time in regardto the sniff mode included in the sniff parameter; and a controller forcontrolling the data communication with the sniff slave apparatus, andcounting a number of the sniff slave apparatus operated in the sniffmode to perform the communication scheduling.

In addition, it is preferable that the master apparatus performs thecommunication with the sniff slave apparatus according to thecommunication scheduling set up in regard to the sniff slave apparatus.Also, it is preferable that the master apparatus performs a round-robinpolling operation that transmits a polling packet so that there is nosniff slave apparatus unable to receive a packet from the masterapparatus during the allocated time of the sniff period in thecommunication operation according to the communication scheduling.Accordingly, it is recommended that the controller sets up a pollingtable including address information with respect to the sniff slaveapparatus for transmitting the polling packet in accordance with theround-robin polling operation, and the parameter storage unit stores thepolling table. The time for the master apparatus to perform theround-robin polling operation is a time that the number of slotsremaining in a corresponding slot of the allocated time of the sniffperiod is equal to the number of sniff slave apparatuses.

It is preferable that the master apparatus transmits the polling packetfrom the sniff slave apparatus that initially transmits the data to themaster apparatus during the allocated time of the sniff period accordingto the round-robin polling operation. In addition, it is advisable thatthe master apparatus transmits the polling packet to corresponding sniffslave apparatuses one at a time. On the other hand, it is recommendedthat the controller ends the communication with the sniff slaveapparatus with respect to the master apparatus, when there are no slotsremaining in the allocated time of the sniff period.

In the meantime, a wireless communication method according to thepresent invention to accomplish the above object includes the steps of:calculating a sniff parameter and a predetermined time for the sniffslave apparatus to perform the communication by commonly using the timewith respect to the master apparatus, when the sniff slave apparatus isset up to be operated in the sniff mode; and performing a mutualcommunication by the master apparatus and the slave apparatus inaccordance with the sniff parameter during the calculated time.

Preferably, after the communication performing step, the wirelesscommunication method further includes the steps of: setting up a pollingtable including a polling packet for providing a connection opportunityfor a sniff slave apparatus that has not received any of the packetsfrom the master apparatus during the allocated time of the sniff periodaccording to the sniff parameter, and an address information withrespect to the sniff slave apparatus to receive the polling packet;judging whether a number of slots remaining in the sniff mode and thenumber of sniff slave apparatuses are equal; and transmitting thepolling packet to the sniff slave apparatus according to the addressinformation, when it is judged that the number of slots remaining in thesniff mode and the number of sniff slave apparatuses are equal.

At this time, the sniff parameter includes at least one among a cyclicinformation, an allocated time information of the sniff period, and astart time information in which the master apparatus communicates withthe sniff slave apparatus operated in the sniff mode.

According to the present invention, the master apparatus sets up thetime for operating the sniff slave apparatuses in the sniff mode, andallows the set-up time to the sniff slave apparatuses so that the sniffslave apparatuses can communicate with the master apparatus. Thus, timefor data transmission in the sniff mode can be saved.

BRIEF DESCRIPTION OF THE DRAWINGS

The above-mentioned objects and the features of the present inventionwill be more apparent by describing the preferred embodiments of thepresent invention by referring to the appended drawings, in which:

FIG. 1 is a block diagram showing the connection status of a Bluetoothapparatus according to an active mode and a sniff mode;

FIG. 2 is a is a block diagram showing a master apparatus of FIG. 1 ingreat detail;

FIG. 3 is a view showing a parameter storage unit of FIG. 2 in greatdetail;

FIG. 4 is a view showing one preferred embodiment of a polling table ofFIG. 3;

FIG. 5 is a view showing a transmission process of a polling packetaccording to a round-robin polling operation when there are three sniffslave apparatuses;

FIG. 6A is a view showing one example of the polling table of the masterapparatus;

FIG. 6B is a view showing one example of the polling packet transmissionaccording to FIG. 6A;

FIG. 7A is a view showing another example of the polling table of themaster apparatus;

FIG. 7B is a view showing the transmission process of the polling packetaccording to FIG. 7A; and

FIG. 8 is a flow chart showing a communication method capable ofperforming a communication by commonly having an operation timeallocated in a sniff mode according to the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

From now on, a communication apparatus of the present invention will bedescribed in great detail by referring to the appended drawings.

FIG. 1 is a block diagram showing a connection status of a Bluetoothapparatus according to an active mode and a sniff mode. A masterapparatus 10 performs an inquiry for sending a driving frequency toslave apparatuses around the master apparatus 10 by using a channel(air). The slave apparatuses 22, 24, 26, 28, 30, 32, 34 perform aninquiry scan for adjusting a synchronism to the transmitted drivingfrequency of the master apparatus 10. Then, the master apparatus 10performs a page for sending a driving timing clock of the masterapparatus 10 to the slave apparatuses 22, 24, 26, 28, 30, 32, 34. Theslave apparatuses 22, 24, 26, 28, 30, 32, 34 perform a page scan foradjusting the synchronism to the transmitted driving timing clock of themaster apparatus 10.

Accordingly, the slave apparatuses 22, 24, 26, 28, 30, 32, 34 connectedwith the master apparatus 10 by the channel are divided into activeslave apparatuses 22, 24, 26, 28 for performing an active modecommunication and sniff slave apparatuses 30, 32, 34 operated in thesniff mode. At this time, the master apparatus 10 and the active slaveapparatuses 22, 24, 26, 28 perform a synchronous one-to-one datatransmission, and also transmit required data through a broadcastingpacket. In the meantime, the master 10 and the sniff slave apparatuses30, 32, 34 perform mutual communication through an allocated time byusing a time excluding a time in which the active mode operation isperformed.

On the other hand, a wireless communication system, in which the sniffslave apparatuses can commonly have the allocated operation time in thesniff mode according to the present invention as shown, includes themaster apparatus 10 for calculating a sniff parameter for communicationin accordance with the sniff mode when a communication mode for a mutualdata exchange by a user is selected to be operated in the sniff mode,and the sniff slave apparatuses 30, 32, 34 for performing mutual datacommunication with the master apparatus 10 by commonly having thecorresponding time set up in accordance with the sniff parameter.Accordingly, the sniff slave apparatuses 30, 32, 34 perform mutualcommunication in accordance with a communication scheduling set up bythe master apparatus 10 while being operated in the sniff mode.

FIG. 2 is a block diagram showing the master apparatus 10 of FIG. 1 ingreat detail. As shown in FIG. 2, the master apparatus 10 comprises aparameter storage unit 16 for storing the sniff parameter, a timecounting unit 14 for counting a time during which the master apparatus10 sends and receives data to and from the sniff slave apparatuses 30,32, 34 operated in the sniff mode, and a controller 12 for controllingthe data communication performed with the sniff slave apparatuses 30,32, 34 according to the sniff mode and counting the number of the sniffslave apparatuses 30, 32, 34 operated in the sniff mode. The sniffparameter refers to a cyclic information that the slave apparatuses 30,32, 34 operate in the sniff mode, an allocated time information of thesniff period, and a start time information. Therefore, the sniff slaveapparatuses 30, 32, 34 perform the sniff operation according to thecommunication scheduling of the master apparatus 10 at the same time bycommonly having the calculated cyclic information of the sniffparameter, the allocated time information of the sniff period, and thestart time information.

The time counting unit 14 counts the time from the start time of thesniff mode in the master apparatus 10, and transmits an end time of theallocated time of the sniff period with respect to the time set upaccording to the sniff mode to the controller 12.

The master apparatus 10 and the sniff slave apparatuses 30, 32, 34perform communication by commonly using the set-up time after setting upa predetermined time for mutual communication between the masterapparatus 10 and the sniff slave apparatuses 30, 32, 34. The masterapparatus 10 has a memory packet for storing the sniff parameter. Themaster apparatus 10 controls the communication by commonly having thesniff slave apparatuses 30, 32, 34 in accordance with the sniffparameter stored in the memory packet.

FIG. 3 is a view showing the parameter storage unit 16 of FIG. 2 ingreat detail. Referring to FIG. 3, the parameter storage unit 16 storesthe sniff parameter 16A and a polling table 16B. The sniff parameter 16Ais parameter information needed for the communication connection of themaster apparatus 10 with the sniff slave apparatuses 30, 32, 34. On theother hand, the master apparatus 10 performs a round-robin pollingoperation that transmits a polling packet to provide an opportunity forconnection with the master apparatus 10 to slave apparatuses that havefailed to establish a communication connection in accordance with thecommunication scheduling. Moreover, the master apparatus 10 sets up thepolling table including the address information with respect tocorresponding sniff slave apparatuses for transmitting the pollingpacket in accordance with the round-robin polling operation. The pollingtable 16B is the address information in regard to the correspondingsniff slave apparatuses set up by the master apparatus 10 to transmitthe polling packet to each of the slave apparatuses. It is preferablethat the polling table, which is set up by the master apparatus 10, isset up consecutively from the corresponding sniff slave apparatuses thathave transmitted the polling table to the master apparatus 10.

In the meantime, the sniff parameter 16A has the cyclic information 16Aaof the sniff mode, and the allocated time information 16Ab of the sniffperiod, and a start time information 16Ac of the sniff mode. The cyclicinformation 16Aa of the sniff mode is the information in regard to thecycle that the master apparatus 10 operates repeatedly according to theset-up sniff mode. The allocated time information 16Ab of the sniffperiod is the information in regard to the time of the period that thesniff slave apparatuses 30, 32, 34 communicate with the master apparatus10. The start time information 16Ac of the sniff mode is the informationin regard to the start time that the sniff slave apparatuses 30, 32, 34communicate with the master apparatus 10.

FIG. 4 is a view showing the preferred embodiment of the polling table16B of FIG. 3. Referring to FIG. 4, the polling table 16B includes thepolling packet ‘P’ transmitted to the sniff slave apparatuses 30, 32,34, and the address information ‘N’ in regard to the corresponding sniffslave apparatuses to which the corresponding polling packet ‘P’ istransmitted.

Referring to FIG. 4, polling packet 1 (P=1) is the table value set up tobe transmitted to the sniff slave apparatus associated with the addressinformation ‘N’ is ‘2’ (N=2) by the master apparatus 10. Polling packet2 (P=2) is the table value set up to be transmitted to the sniff slaveapparatus associated with the address information ‘N’ is ‘4’ (N=4) bythe master apparatus 10. Polling packet 3 (P=3) is the table value setup to be transmitted to the sniff slave apparatus associated with theaddress information ‘N’ is ‘3’ (N=3) by the master apparatus 10. Pollingpacket 4 (P=4) is the table value set up to be transmitted to the sniffslave apparatus associated with the address information ‘N’ is ‘5’ (N=5)by the master apparatus 10. Polling packet ‘n’ (P=n) is the table valueset up to be transmitted to the sniff slave apparatus associated withthe address information ‘N’ is ‘4’ (N=4) by the master apparatus 10.Accordingly, the master apparatus 10 transmits the polling packet to thesniff slave apparatus having a corresponding address in accordance withthe address information ‘N’.

FIG. 5 is a view showing the transmission process of the polling packetaccording to the round-robin operation when there are three sniff slaveapparatuses. In FIG. 5, a period for data communication of the sniffslave apparatuses 30, 32, 34 with the master apparatus 10 in the entireperiod according to a time axis (t) is a sniff mode period. The sniffmode period is divided into a data transmission period and a round-robinpolling period. The data transmission period is the period for mutualdata transmission between the master apparatus 10 and the sniff slaveapparatuses 30, 32, 34 according to the communication scheduling. Theround-robin polling period is the period for the master apparatus 10 toreceive a response after transmitting the polling packet.

Referring to FIG. 5, when the master apparatus 10 transmits the pollingpacket to sniff slave apparatus associated with address 1 (N=1) withinthe round-robin polling period, the sniff slave apparatus associatedwith address 1 receives the polling packet that the master apparatus 10has transmitted. At this time, the sniff slave apparatus associated withaddress 1 that has received the polling packet transmitted from themaster apparatus 10 transmits some data such as a null packet or a datapacket to the master apparatus 10. In other words, only thecorresponding sniff slave apparatus that has received the polling packetof the master apparatus 10 within the round-robin polling period or hasreceived the data packet of the master apparatus 10 within the allocatedtime of the sniff period can transmit the data packet or the null packetto the master apparatus 10 in a next slot.

FIG. 5 shows various time axes in regard to the time axis (t) in theround-robin polling period: a time axis (M_(T)) illustrates the masterapparatus 10 transmitting the polling packet; a time axis (M_(R))illustrates the master apparatus 10 receiving the null packettransmitted from the sniff slave apparatuses; a time axis (S_(T))illustrates the sniff slave apparatuses transmitting the null packet tothe master apparatus 10; and a time axis (S_(R)) illustrates the sniffslave apparatuses receiving the polling packet transmitted from themaster apparatus 10.

FIG. 6A is a view showing one example of the polling table of the masterapparatus 10, and FIG. 6B is a view showing one example of thetransmission of the polling packet according to FIG. 6A. First of all,FIG. 6A is the table value set up to transmit the polling packet 2 (P=2)to the sniff slave apparatus corresponding to address ‘2’ (N=2).Therefore, as shown in FIG. 6B, the master apparatus 10 transmits thepolling packet to the sniff slave apparatus 44 corresponding to theaddress information (N) is ‘2’ (N=2) among the slave apparatuses 42, 44,46, 48.

FIG. 7A is a view showing another example of the polling table of themaster apparatus 10, and FIG. 7B is a view showing the process of thepolling packet transmission according to FIG. 7A. First of all, FIG. 7Ais the table value set up to transmit the polling packet to the sniffslave apparatus corresponding to the address information (N). Accordingto FIG. 7A, the table value is set up to consecutively transmit thepolling packet to the sniff slave apparatuses corresponding to theaddress information (N) is ‘4’ (N=4), ‘2’ (N=2), and ‘3’ (N=3).

As shown in FIG. 7B, the master apparatus 10 first transmits the pollingpacket to the sniff slave apparatus 46 corresponding to the addressinformation (N) is ‘4’ (N=4) among the slave apparatuses 42, 44, 46, 48.Then, the master apparatus 10 transmits the polling packet to the sniffslave apparatus 44 corresponding to the address information (N) is ‘2’(N=2). Next, the master apparatus 10 transmits the polling packet to thesniff slave apparatus 48 corresponding to the address information (N) is‘3’ (N=3), after transmitting the polling packet to the sniff apparatus44 that the address information (N) is ‘2’ (N=2).

Accordingly, the master apparatus 10 performs communication with thesniff slave apparatuses 42, 44, 46, 48 during the allocated time of thesniff period. Additionally, the master apparatus 10 can maintain thecommunication connection with sniff slave apparatuses that have notreceived any of packets from the master apparatus 10 during theallocated time of the sniff period by setting up the round-robin pollingperiod within the allocated time of the sniff period, transmitting thepolling packet to each of the sniff slave apparatuses 42, 44, 46, 48,and receiving the packet from the sniff slave apparatuses 42, 44, 46, 48according to the transmission, to provide a connection opportunity tothe sniff slave apparatuses that have failed to communicate with themaster apparatus 10 during the allocated time of the sniff period.

FIG. 8 is a flow chart showing a communication method for performing thecommunication by commonly having the allocated time of the sniff periodaccording to the present invention. First of all, the master apparatus10 judges whether the operation mode of the slave apparatuses is thesniff mode in accordance with the control of a user (S 10). It ispreferable that a predetermined time is set up so that the slaveapparatuses can communicate with the master apparatus 10 during theallocated time of the sniff period when the slave apparatuses areoperated in the sniff mode before the step 10.

When the master apparatus 10 judges that the operation mode of the slaveapparatuses is not the sniff mode in the step 10, the master apparatus10 performs an operation corresponding to the operation mode of theslave apparatuses selected by the user (S 12). In the step 10, when theoperation mode of the slave apparatuses is judged as the sniff mode, themaster apparatus 10 performs the data transmission with the sniff slaveapparatuses 42, 44, 46, 48. At this time, the master apparatus 10 judgeswhether there is any data transmitted from the sniff slave apparatuses42, 44, 46, 48 (S 16). When it is judged that there is no transmitteddata, the master apparatus 10 performs the step 14.

When it is judged that there is data transmitted from the sniff slaveapparatuses 42, 44, 46, 48 in the step 16, the master apparatus 10calculates the number of slots (Sr) remaining of all the slots (St) setup as the allocated time of the sniff period (S 18). The number of slots(Sr) remaining in the allocated time of the sniff period in the masterapparatus 10 can be calculated by subtracting the time of thecommunication with the sniff slave apparatuses 42, 44, 46, 48 from thenumber of entire slots (St).

The master apparatus 10 judges that the subtracted value is ‘0’ bycalculating the number (Sn) of the sniff slave apparatuses connectedwith the master apparatus 10 from the number of remaining slots (Sr)during the mutual data transmission with the sniff slave apparatuses 42,44, 46, 48 (S 20). In other words, the master apparatus 10 judgeswhether the number of remaining slots (Sr) and the number of the sniffslave apparatuses are equal.

When it is judged that the number of remaining slots (Sr) is differentfrom the number of the sniff slave apparatuses (Sn) in the step 20, themaster apparatus 10 performs the steps 14 through 18. When it is judgedthat the number of remaining slots (Sr) and the number of the sniffslave apparatuses (Sn) are equal in the step 20, the master apparatus 10performs the round-robin polling operation for transmitting the pollingpacket to the sniff slave apparatus having the corresponding addressbased on the set up polling table (S 22). The master apparatus 10 judgeswhether there is any remained slot while performing the round-robinpolling operation (S 24).

When it is judged that there is a remaining slot in the step 24, themaster apparatus 10 performs the operation of the step 22. When it isjudged that there is no remaining slot in the step 24, the masterapparatus 10 ends the communication in the sniff mode with the sniffslave apparatuses 42, 44, 46, 48, and performs data transmission with aslave that is the active mode (S 26).

Accordingly, as the communication with the sniff slave apparatusescontrolled by the master apparatus 10 is commonly used during theallocated time of the sniff mode, the sniff parameter that is operationinformation according to the sniff mode can become simpler. Moreover, asthe polling packet is transmitted to the respective sniff slaveapparatuses from the time that the number of the remaining slot (Sr) andthe number of the sniff slave apparatuses (Sn) are equal in the set-uptime of the sniff mode, the sniff slave apparatuses can be preventedfrom not being connected with the master apparatus 10 during theallocated time of the sniff period.

According to the present invention, since the master apparatus sets upthe time for the communication with the sniff slave apparatuses, andallows the sniff slave apparatuses to commonly use the set-up time, timefor mutual communication in the allocated time of the sniff period canbe saved. Further, the amount of memory needed for the master apparatus10 also can be reduced, as the master apparatus 10 provides the commonsniff parameter to the sniff slave apparatuses even when there areplurality of sniff slave apparatuses. In addition, since the pollingpacket based on the polling table is transmitted to the correspondingsniff slave apparatuses from the time that the number of the remainingslots (Sr) and the number of the sniff slave apparatuses (Sn) are equalduring the allocated time of the sniff period, sniff slave apparatusescan be prevented from not being connected with the master apparatus 10by not being transmitted a packet from the master apparatus 10 duringthe allocated time of the sniff period.

So far, the preferred embodiments of the present invention have beenillustrated and described. However, the present invention is not limitedto the preferred embodiments described here, and someone skilled in theart can modify the present invention without departing from the spiritof the present invention claimed in the claims.

1. A wireless communication system, comprising: a master apparatus for calculating a sniff parameter including a time of a sniff period capable of performing a communication by allowing a corresponding device to commonly use the time in a sniff mode when a communication mode for mutual data transmission is selected by a user to be operated in the sniff mode; and one or more sniff slave apparatuses for performing the mutual data transmission with the master apparatus by commonly using the time calculated in accordance with the sniff parameter, wherein the master apparatus performs a communication scheduling for data communication of the one or more sniff slave apparatuses, when the sniff parameter is calculated, and wherein the master apparatus comprises: a parameter storage unit for storing the sniff parameter; a time counting unit for allowing the master apparatus to count a time during an allocated time of a sniff period according to the sniff mode based on an operation time in regard to the sniff mode included in the sniff parameter; and a controller for controlling the data communication with the one or more sniff slave apparatuses, and counting a number of the one or more sniff slave apparatuses operated in the sniff mode to perform the communication scheduling.
 2. A wireless communication system, comprising: a master apparatus for calculating a sniff parameter including a time of a sniff period capable of performing a communication by allowing a corresponding device to commonly use the time in a sniff mode, when a communication mode for mutual data transmission is selected by a user to be operated in the sniff mode; and one or more sniff slave apparatuses for performing the mutual data transmission with the master apparatus by commonly using the time calculated in accordance with the sniff parameter, wherein the master apparatus performs a communication scheduling for data communication of the one or more sniff slave apparatuses, when the sniff parameter is calculated, wherein the sniff parameter includes at least one among a cyclic information, an allocated time information of the sniff period, and a start time information in which the one or more sniff slave apparatuses are operated in the sniff mode, and wherein the master apparatus performs the communication with the one or more sniff slave apparatuses according to the communication scheduling set up in regard to the one or more sniff slave apparatuses, and performs a round-robin polling operation that transmits a polling packet so that there is no sniff slave apparatus unable to receive a packet from the master apparatus during the allocated time of the sniff period in the communication operation according to the communication scheduling.
 3. The wireless communication system of claim 2, wherein the controller sets up a polling table including an address information with respect to the one or more sniff slave apparatuses for transmitting the polling packet in accordance with the round-robin polling operation, and the parameter storage unit stores the polling table.
 4. The wireless communication system of claim 3, wherein the time for the master apparatus to perform the round-robin polling operation is a time that a number of slots remaining in a corresponding slot of the allocated time of the sniff period is equal to a number of the one or more sniff slave apparatuses.
 5. The wireless communication system of claim 4, wherein the master apparatus transmits the polling packet from the sniff slave apparatus that initially transmits the data to the master apparatus during the allocated time of the sniff period according to the round-robin polling operation.
 6. The wireless communication system of claim 5, wherein the master apparatus transmits the polling packet to a corresponding sniff slave apparatus one at a time respectively.
 7. The wireless communication system of claim 6, wherein the controller ends the communication with the one or more sniff slave apparatuses with respect to the master apparatus, when there is no slot remaining in the allocated time of the sniff period.
 8. A wireless communication method between a master apparatus that mutually communicates wirelessly with one or more sniff slave apparatuses during an allocated time of a sniff period, including the steps of: calculating a sniff parameter and a predetermined time for the one or more sniff slave apparatuses to perform the mutual communication by commonly using the time with respect to the master apparatus, when the one or more sniff slave apparatuses are set up to be operated in the sniff mode; and performing the mutual communication by the master apparatus and the one or more sniff slave apparatuses in accordance with the sniff parameter during the calculated time, after the communication performing step, further including the steps of: setting up a polling table including a polling packet for providing a connection opportunity in regard to the sniff slave apparatus that has not received a packet from the master apparatus during the allocated time of the sniff period according to the sniff parameter, and an address information with respect to the sniff slave apparatus to receive the polling packet; judging whether a number of slots remaining in the sniff mode and a number of the sniff slave apparatus are equal; and transmitting the polling packet to the sniff slave apparatus according to the address information, when it is judged that the number of slots remaining in the sniff mode and the number of the one or more sniff slave apparatuses are equal. 